BINDING FORCES CONTRIBUTING TO REVERSED-PHASE LIQUID CHROMATOGRAPHIC RETENTION ON A BETA-CYCLODEXTRIN BONDED PHASE

摘要

Reversed-phase liquid chromatographic (RPLC) capacity factors for a number of organic solutes on a beta-cyclodextrin (beta-CD) bonded phase column in pure water mobile phase (k(w)') were compared with formation constants of inclusion complexes (K-f) between beta-CD and the solutes based on the linear solvation energy relationship (LSER) in order to understand the types and relative strengths of various intermolecular forces between CD and the guest solute affecting the stability of inclusion complexes and hence retention in RPLC. A close fit of capacity factors (k(w)') with complexation constants indicated that inclusion complexation is the major driving force in retention on the beta-CD-bonded phase in RPLC. Comparison of LSERs for K-f and k(w)' showed that an increasing guest molecular size stabilizes the complex by virtue of increasing dispersive interactions between the hydrophobic interior of CD cavity and the guest and hence increases the RPLC retention, and that increasing guest dipolarity and hydrogen bond (HE) acceptor basicity lead to a decrease in the stability of the complex due to the stronger dipolar and HE interactions with water, and hence decrease the retention.